1. Field of the Invention
The present invention relates to a sensor device for detecting small angular position changes and, more particularly, to a sensor device for detecting angular position changes of mechanical parts that rotate relative to each other, especially those angle changes due to the torsion experienced by an axle.
2. Prior Art
From U.S. Pat. No. 5,501,110, a sensor device is already known in which the torque transmitted to an axle is to be detected. The torque is determined by the torsion or the angle of rotation of the ends of the axle and a constant that depends on the material and geometry of the axle. Two magnets and one Hall sensor opposite each magnet are mounted on two disks that each rotate with the axle and are mechanically solidly coupled to the ends of the axle.
For instance, to detect the torque acting on a steering wheel axle of a motor vehicle while the steering wheel is rotating, very small angle changes in both directions of rotation of the steering wheel must be measured. Evaluating the changes in the field originating at the magnets therefore requires an extremely sensitive and also temperature-stable measurement device.